1. Field of the Invention
The present invention relates to a comparator for measuring dimension difference of a workpiece relative to a standard-size piece, which can be used for measuring dimension difference of a workpiece relative to a master workpiece.
2. Description of Related Art
A comparator has been used for measuring dimension difference of a workpiece relative to a master workpiece.
A conventional comparator has a frame, a spindle and an anvil supported by the frame and moved toward and away with each other by axial movement thereof, a biasing means provided to the frame for biasing the anvil toward the spindle, a release for retracting the anvil relative to the spindle against the biasing means, an indicator provided to the frame and an indicator driver provided to the frame for transmitting the movement of the anvil toward the indicator.
In order to measure dimension difference of a workpiece relative to a master workpiece, the anvil is initially retracted away from the spindle by the release. Then, after interposing a master workpiece between the anvil and the spindle, the release is freed to advance the anvil toward the spindle by the biasing means, so that the master workpiece is held between the anvil and the spindle. At this time, in order to conduct zero adjustment of an index, the spindle is moved in axial direction, or alternatively, a graduation plate of the indicator is rotated. Subsequently, after the anvil is retracted by the release to detach the master workpiece from the comparator, a workpiece is held and measured between the anvil and the spindle in the same operation. Accordingly, the value of the indicator can be measured as dimension difference of the workpiece relative to the master workpiece.
Incidentally, since the above-described comparator holds and measures the workpiece and the master workpiece between the spindle and the anvil, accurate measurement sometimes cannot be conducted according to material of the workpiece. Especially, in measuring a soft, for instance, resin-made workpiece, the workpiece can be deformed on account of the measuring force, thus failing to conduct accurate measurement.
Accordingly, an object of the present invention is to provide a comparator capable of accurate measurement irrespective of material of the workpiece.
Further, the above-described comparator may sometimes be used at a work site where droplet of grinding coolant liquid etc. is directly showered and a workpiece adhered with the coolant liquid is often directly measured. Accordingly, foreign substance such as grinding coolant and water can invade into the indicator driver, thus causing malfunction and deterioration of accuracy.
Another object of the present invention is to provide a comparator capable of preventing invasion of foreign substance and maintaining movement and measurement accuracy.
The present invention includes following arrangement in order for a comparator to be capable of accurate measurement irrespective of material of a workpiece.
A comparator according to an aspect of the present invention has: a frame; a spindle and an anvil supported by the frame to be advanceable and retractable in the axial direction thereof to move toward and away from each other; a biaser provided to the frame for biasing the anvil toward the spindle; a release for retracting the anvil relative to the spindle against the biaser; an indicator provided on the frame; and an indicator driver provided to the frame for transmitting the movement of the anvil to the indicator, where a seal member interposed at a border between an exterior surface of the frame and at least one of the anvil, the biaser, the release and the indicator.
According to the above aspect of the present invention, though there can be slight gap between the frame and the anvil, the biasing means, the release and the indicator, since the gap is sealed by the seal member, foreign substance such as grinding coolant and water can be prevented from invading into the indicator driver, thus maintaining precise movement and measurement accuracy. Accordingly, durability and reliability of the comparator can be enhanced.
In the above arrangement, the seal member may preferably be cylindrical and expandable, the cylindrical expandable seal member having a first end connected to an outer circumference of the inner end of the anvil and a second end connected to the frame around the outer circumference of the anvil.
Accordingly, since the cylindrical seal member is used, the gap between the anvil and the frame can be completely covered, thus preventing invasion of the foreign substance in the gap. Further, since the seal member is expandable, the seal member expands and contracts in accordance with the axial advancement and retraction of the anvil, thus not impairing the movement of the anvil. Therefore, the invasion of the foreign substance into the frame can be prevented while securing smooth operation of the anvil.
In the above aspect of the present invention, a cap may preferably be screwed to the frame opposing the outer end of the anvil, where the biaser is interposed between the cap and the anvil and wherein a seal member is provided between the frame and the cap.
According to the above arrangement, since the biaser for biasing the anvil toward the spindle is held by the cap screwed to the frame and the gap between the cap and the frame is sealed by the seal member, the invasion of the foreign substance into the frame can be prevented. Further, since the cap is screwed to the frame, the biaser can be easily exchanged by attaching and detaching the cap, so that the biasing force can be adjusted by exchanging the biaser.
In the above aspect of the present invention, the release may preferably project from an inside of the frame toward the outside, the release having a manipulation knob capable of axial advancement and retraction and an interlocking arm provided between the manipulation knob and the anvil for retracting the anvil relative to the spindle interlocking with the manipulation of the manipulation knob, where a first end of a cylindrical expandable seal member may preferably be connected to the frame on the outer circumference of the inner end of the manipulation knob and a second end of a cylindrical expandable seal member may preferably be connected to the outer circumference of the outer end of the manipulation knob.
Accordingly, since the cylindrical seal member is used, the gap between the manipulation knob and the frame can be completely covered, so that invasion of the foreign substance into the gap can be prevented. Further, since the seal member is expandable, the seal member expands and contracts in accordance with axial advancement and retraction of the manipulation knob, thus not impairing the operation of the manipulation knob. Therefore, the invasion of the foreign substance into the frame can be prevented while securing smooth operation of the manipulation knob.
In the above aspect of the present invention, the indicator may preferably include: a case; a graduation plate and an index installed in the case; a transparent plate covering an opening of the case; and an exterior frame for holding the transparent plate to the case, where a seal member is provided between the case and the transparent plate and between the exterior frame and the frame.
Accordingly, though the case, the transparent plate and the exterior frame are independent of the frame, the invasion of the foreign substance into the frame can be prevented by sealing the gap between the case and the transparent plate with the seal member, and the invasion of the foreign substance into the indicator driver can be prevented by sealing the gap between the exterior frame and the frame with the seal member.
In another aspect of the present invention, a comparator capable of preventing invasion of the foreign substance and maintaining operation and measurement accuracy includes following arrangement.
A comparator according to the above aspect of the present invention includes: a frame; a spindle and an anvil supported by the frame to be advanceable and retractable in the axial direction thereof to move toward and away from each other; a biaser provided to the frame for biasing the anvil toward the spindle; a release for retracting the anvil relative to the spindle against the biaser; an indicator provided on the frame; and an indicator driver provided to the frame for transmitting the movement of the anvil to the indicator, the comparator being characterized in that a biasing force adjuster for varying the biasing force of the biaser is provided.
According to the above aspect of the present invention, since the measurement force can be reduced to a range without affecting the shape of the workpiece by the biasing force adjuster, even when the workpiece of soft material, the workpiece is not deformed on account of measuring force, thus enabling accurate measurement and enhancing reliability of the comparator.
In the above aspect of the present invention, the biasing force adjuster may preferably include: a sleeve screwed to the frame opposing an outer end of the anvil; and an adjusting knob screwed to the sleeve, the biaser being interposed between the adjusting knob and the anvil.
Accordingly, the distance from the anvil to the adjusting knob can be changed by rotating the adjusting knob, in other words, the length of the biaser can be changed little by little, the measuring force can be minutely adjusted.
In the above aspect of the present invention, a graduation indicating magnitude of the biasing force may preferably be provided on the outer circumference of the sleeve along the axial direction thereof.
Accordingly, since the graduation is provided on the outer circumference of the sleeve in the axial direction, the distance from the anvil to the adjusting knob can be accurately calculated, so that the measurement force can be adjusted while checking magnitude thereof.
Further, a comparator according to still another aspect of the present invention includes following arrangement in order to conduct accurate measurement without being restricted by the material of the workpiece and prevent the invasion of the foreign substance to prevent operation and measurement accuracy thereof.
A comparator according to the above aspect of the present invention includes: a frame; a spindle and an anvil supported by the frame to be advanceable and retractable in the axial direction thereof to move toward and away from each other; a biaser provided to the frame for biasing the anvil toward the spindle; a release for retracting the anvil relative to the spindle against the biaser; an indicator provided on the frame; and an indicator driver provided to the frame for transmitting the movement of the anvil to the indicator, the comparator being characterized in that a seal member and a biasing force adjuster for varying the biasing force of the biaser are provided on the border between an outer surface of the frame and at least one of the anvil, the biaser, the release and the indicator.
According to the above aspect of the present invention, though there can be slight gap between the frame and the anvil, the biaser, the release and the indicator, the gap is sealed by the seal member, the foreign substance such as the grinding coolant and water at work site can be prevented from invading into the indicator driver, thus maintaining operation and measurement accuracy. Accordingly, durability and reliability of the comparator can be improved.
In addition, since the measuring force can be decreased to a range without influencing on the shape of the workpiece by the biasing force adjustor, the workpiece is not deformed on account of the measuring force, so that accurate measurement is possible and reliability of the comparator can be enhanced.